Permanent magnet alloys



PERMANENT MAGNET ALLOYS Louis Glaser, Colombes, France N Drawing. Application April 8, 1952, Serial No. 281,220

7 Claims. (Cl. 75123) This invention relates to permanent magnets made of iron-base alloys.

Iron-base alloys containing about 20% of nickel and about 10 to 12% of aluminum by weight are known.

Alloys according to my invention have magnetic properties which are very much superior to the known alloys. Alloys according to my invention are free of oxygen and thus present many advantages.

My alloy contains iron as a base and one or more rare earths, such as cerium, neodymium, praseodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, lanthanum and yttrium.

As examples, I can add to iron a percentage by weight of 2.5% of cerium, or I can add to the iron of cerium, 1% of neodymium, 0.25% of samarium, and 0.05% of gadolinium. All percentages mentioned herein are by weight.

The rare earths used in making my alloy can be contained, for example, in the waste resulting from the production of cerium, thorium, uranium, tin, tungsten or yttrium.

In accordance with my invention, I can replace partially or totally the aluminum content of iron, nickel and aluminum alloys with one or more rare earths. Thus, I have obtained very good results with an alloy of iron as a base and containing 25% of nickel, of alumnum, 2.5 of lanthanum, 0.5% of neodymium, and 0.1% of Samarium. This alloy gave a coercive force of 750 oersteds with a residual flux density of 5000 gauss.

One alloy according to my invention consists of iron as a base, about 20% of nickel, and from 10 to 12% of a combination of aluminum and one or more rare earths. Thus, I can use 8% of one or more rare earths and from 2 to 4% of aluminum, together with about 20% of nickel, the balance being iron.

Excellent results were obtained by replacing one part of aluminum with scandium, yttrium or lanthanum, alone or in combination. These three elements have melting points higher than that of aluminum; the melting points of the two first mentioned elements being about 00 C., and the melting point of lanthanum being about 900 C.

Nickel can be substituted partially or totally by cobalt. Yttrium or lanthanum each form compounds with aluminum, iron, nickel and cobalt. It should be noted that alloys containing rare earths not only allow obtaining per manent magnets having excellent magnetic properties (residual flux density and coercive force), but furthermore, the rare earths destroy oxides and other inclusions sometimes existing in alloys having iron, nickel or cobalt as a base.

My alloy can contain a certain percentage of titanium, zirconium, vanadium, copper or niobium. All of these elements can react with the rare earths.

2,813,789 Patented Nov. 19, 1957 ice The magnetic properties such as residual flux density and coercive force of magnets made from alloys according to my invention, can be improved by adding one or more rare earths chosen especially according to their magnetic momentum which varies according to their position in the periodic system of elements. The alloys of my invention may be submitted to a thermal treatment either by heating them in a suitable metallic mold or shell or by hardening, as for instance by a special heat treatment corresponding to the particular Curie point of the alloy.

The alloys of my invention can contain only iron together with one or more rare earths, or the alloys can contain in addition not more than about 12% of aluminum. Furthermore, the alloys can contain up to 30% I of cobalt or nickel or both. Also, the alloys can contain one or more of the elements titanium, zirconium, vanadium, copper or niobium.

I claim:

1. A permanent magnet made of an alloy consisting of iron and from 2.5% to 12% of at least one rare earth.

2. A permanent magnet made of an alloy consisting of iron, an efiective amount up to 12% of aluminum, and from 2.5% to 12% of at least one rare earth.

3. A permanent magnet made of an alloy consisting of iron, an eifective amount up to 12% of aluminum, an effective amount up to 30% of a member of the class consisting of nickel and cobalt, and from 2.5% to 12% of at least one rare earth.

4. A permanent magnet made of an alloy consisting of iron, a member of the class consisting of nickel and cobalt in an amount of 20% to 25%, aluminum and at least one rare earth, the rare earth amounting to at least 2.5%, the sum of the rare earth and aluminum being between 10% and 12%.

5. A permanent magnet according to claim 4, wherein the alloy contains from 2% to 4% of aluminum.

6. A permanent magnet made of an alloy consisting of about 20% to 25% of a member of the class consisting of nickel and cobalt, about 2% to 4% aluminum, and about 8% of at least one rare earth, the balance being all iron.

7. A permanent magnet made of a ferrous base alloy consisting essentially of iron, up to 30% of a member of the class consisting of nickel and cobalt, and from 2.5% to 12% of at least one rare earth.

References Cited in the file of this patent UNITED STATES PATENTS 1,641,752 Flintermann Sept. 6, 1927 2,061,370 Rohn NOV. 17, 1936 2,239,144 Dean et a1 Apr. 22, 1941 2,360,717 Phelps Oct. 17, 1944 FOREIGN PATENTS 471,051 Great Britain Aug. 20, 1937 118,104 Sweden Feb. 11, 1947 OTHER REFERENCES Zeitschrift fiir Anorganische Chemie, Band 99, pages 30 and 38-41, incl.; pub. 1917.

Molybdenum, Cerium and Related Alloy Steels, pages 128 and 129. Edited by Gillett and Mack. Published in 1925 by the Chemical Catalog Go, New York.

Article-Permanent Magnet Alloys, by Underhill. Reprinted from Electronics, January 1948 (4 pages.)

Metal Handbook, 1948 edition, page 601. Published in 1948 by the American Society for Metals, Cleveland, Ohio. 

1. A PERMENT MAGNET MADE OF AN ALLOY CONSISTING OF IRON AND FROM 2.5% TO 12% OF AT LEAST ONE RARE EARTH. 